(1) Field of the Invention
The invention relates to electron beam devices and is directed more particularly to a method for forming a field emission flat panel and to the panel formed thereby.
(2) Description of the Prior Art
Field emission flat panels are known in the art. Such devices have been disclosed in prior patents, including U.S. Pat. No. 3,755,704, issued Aug. 28, 1973, to Charles A. Spindt et al; U.S. Pat. No. 4,307,507, issued Dec. 29, 1981, to Henry F. Gray et al; U.S. Pat. No. 4,908,539, issued Mar. 13, 1990, to Robert Meyer; and U.S. Pat. No. 5,210,472, issued May 11, 1993, to Stephen L. Casper et al. The devices have found wide acceptance in light-weight portable displays.
Conventional microfabricated field emission cathode arrays and powder phosphor anode screens have been widely used to manufacture the field emission flat panel displays. The cathode processing usually is carried out in accordance with the teachings of Spindt (U.S. Pat. No. 3,755,704) or Gray (U.S. Pat. No. 4,307,507). Parallel spaced conductors are first formed on a substrate and act as cathode columns (emitter base electrode) of the display. Sharp pointed emitters are formed on the cathode columns. Another set of parallel spaced conductors, known as gate rows, is separated by a dielectric layer and formed perpendicular to the cathode column. The gate rows are opened with apertures and cavities for each emitter. The device is operated by inputting voltage signals to the columns and rows through matrix-addressing. When the gate-to-emitter voltage differential at a particular intersection of a column and a row is sufficiently high, electron emission occurs at the emitter tip. The emitted electrons pass the gate and strike the phosphor screen anode which is closely mounted above the gate and biased with a higher potential. A display element is then lighted up as a result of the electron excitation of the phosphorous material.
A complex spacer manufacturing process is required in order to provide spacer means to support the anode screen and the cathode part inasmuch as the space therebetween is evacuated. The spacer architecture occupies a considerable display area, although efforts are made to confine the spacers between gate rows. It becomes a limitation factor for higher resolution displays. Further, over time the spacer becomes contaminated with emitter material. Accordingly, there is a need for a method for forming flat panel displays in which the usual spacer is not required, but in which the necessary support is provided, as well as electrical isolation of the gate means.
The anode screen typically is a conventional powder phosphor screen. However, the phosphor material decomposes under constant bombardment by high energy electrons. Particles released from phosphors are known to deposit on the emitter surface and cause tip contamination and even termination. Accordingly, there is a need for a method for forming flat panel displays in which the usual powder phosphor screen is not utilized, but wherein a phosphor screen is provided for electron excitation.